Format build-tools and build-tools-internal (#78910)

Our spotless configuration wasn't being applied to `build-tools`
and `build-tools-internal`. Move the Spotless configuration to a
Java plugin in `build-conventions`, and apply it everywhere.

This resulted in a lot more Java files being subject to formatting,
so I added more exclusions to the list.

Also remove the `paddedCell` stuff, we've never needed it.

CONTRIBUTING.md

@@ -193,14 +193,14 @@ need them.
    2. Click "Use the Eclipse Code Formatter"
    3. Under "Eclipse formatter config", select "Eclipse workspace/project
       folder or config file"
-   4. Click "Browse", and navigate to the file `build-tools-internal/formatterConfig.xml`
+   4. Click "Browse", and navigate to the file `build-conventions/formatterConfig.xml`
    5. **IMPORTANT** - make sure "Optimize Imports" is **NOT** selected.
    6. Click "OK"
 
 Note that only some sub-projects in the Elasticsearch project are currently
 fully-formatted. You can see a list of project that **are not**
 automatically formatted in
-[build-tools-internal/src/main/groovy/elasticsearch.formatting.gradle](build-tools-internal/src/main/groovy/elasticsearch.formatting.gradle).
+[FormattingPrecommitPlugin.java](build-conventions/src/main/java/org/elasticsearch/gradle/internal/conventions/precommit/FormattingPrecommitPlugin.java).
 
 ### Importing the project into Eclipse
 
@@ -234,15 +234,15 @@ Next you'll want to import our auto-formatter:
  - Select **Window > Preferences**
  - Select **Java > Code Style > Formatter**
  - Click **Import**
- - Import the file at **build-tools-internal/formatterConfig.xml**
+ - Import the file at **build-conventions/formatterConfig.xml**
  - Make sure it is the **Active profile**
 
 Finally, set up import order:
 
  - Select **Window > Preferences**
  - Select **Java > Code Style > Organize Imports**
  - Click **Import...**
- - Import the file at **build-tools-internal/elastic.importorder**
+ - Import the file at **build-conventions/elastic.importorder**
  - Set the **Number of imports needed for `.*`** to ***9999***
  - Set the **Number of static imports needed for `.*`** to ***9999*** as well
  - Apply that
@@ -279,11 +279,12 @@ form.
 Java files in the Elasticsearch codebase are automatically formatted using
 the [Spotless Gradle] plugin. All new projects are automatically formatted,
 while existing projects are gradually being opted-in. The formatting check
-can be run explicitly with:
+is run automatically via the `precommit` task, but it can be run explicitly with:
 
     ./gradlew spotlessJavaCheck
 
-The code can be formatted with:
+It is usually more useful, and just as fast, to just reformat the project. You
+can do this with:
 
     ./gradlew spotlessApply
 
@@ -304,10 +305,9 @@ Please follow these formatting guidelines:
 * Wildcard imports (`import foo.bar.baz.*`) are forbidden and will cause
   the build to fail.
 * If *absolutely* necessary, you can disable formatting for regions of code
-  with the `// tag::NAME` and `// end::NAME` directives, but note that
-  these are intended for use in documentation, so please make it clear what
-  you have done, and only do this where the benefit clearly outweighs the
-  decrease in consistency.
+  with the `// @formatter:off` and `// @formatter:on` directives, but
+  only do this where the benefit clearly outweighs the decrease in formatting
+  consistency.
 * Note that Javadoc and block comments i.e. `/* ... */` are not formatted,
   but line comments i.e `// ...` are.
 * Negative boolean expressions must use the form `foo == false` instead of

build-conventions/build.gradle

@@ -49,6 +49,10 @@ gradlePlugin {
             id = 'elasticsearch.versions'
             implementationClass = 'org.elasticsearch.gradle.internal.conventions.VersionPropertiesPlugin'
         }
+        formatting {
+            id = 'elasticsearch.formatting'
+            implementationClass = 'org.elasticsearch.gradle.internal.conventions.precommit.FormattingPrecommitPlugin'
+        }
     }
 }
 
@@ -62,6 +66,9 @@ dependencies {
     api 'gradle.plugin.com.github.jengelman.gradle.plugins:shadow:7.0.0'
     api 'org.apache.rat:apache-rat:0.11'
     compileOnly "com.puppycrawl.tools:checkstyle:8.42"
+    api('com.diffplug.spotless:spotless-plugin-gradle:5.16.0') {
+      exclude module: "groovy-xml"
+    }
 }
 
 project.getPlugins().withType(JavaBasePlugin.class) {